I have this niggling feeling you’re looking for ways to set up your story before it happens. As in, Psst! Hey, Reader, let me tell you something about the character before you start. Don’t do that. You have plenty of time to slip them background info once they care about your protagonist and the problems ahead of her. If they don’t care about her, they won’t give a fig about the things that happened in her past to make her who she is today. Instead, open with your character doing something that reveals her personality and hints at her problems. Then sprinkle in the background essentials, teasing them out with little references and then doing a Grand Reveal in a clever, unexpected way. Flashbacks are often big backstory dumps, so use them sparingly and with caution. Prologues are okay as long as you’re not just looking for a dumping method that doesn’t being with the letter “f”. The prologue must be entertaining in its own right. It’s not a free Psst! Hey Reader! moment. That’s when prologues become “deadly.” Readers want action in the first words, not explanation.